Cluster model for radiative transition probabilities of d5 ions in tetrahedralsymmetry: Case of Mn2+ in the common cation series ZnS, ZnSe, and ZnTe

Mechanisms of manganese-assisted non-radiative recombination in Cd(Mn)Se/Zn(Mn)Se quantum dots

“…The transition is spin and parity forbidden so that the spin-orbit interaction and admixture of p states to d msz should be taken into account otherwise d rγS ′ z ,Sz = 0. According to the model of Boulanger et al 45…”

Mn2+‐Doped CdSe Quantum Dots: New Inorganic Materials for Spin‐Electronics and Spin‐Photonics

“…6 A 1 transition is partially overcome by spin-orbit coupling at the Mn 2þ (z % 300 cm À1 for the free Mn 2þ ion) and at the anion through covalency, particularly for selenides and tellurides (e.g., z(S 2À ) % 300 cm À1 , z(Se 2À ) % 1400 cm À1 , z(Te 2À ) % 3600 cm À1 ). [60] At elevated Mn 2þ concentrations, Mn 2þ -Mn 2þ exchange interactions also provide a mechanism for circumventing the spin forbiddeness because the transition only needs to conserve the total spin of the cluster. [61,62] These mechanisms are not usually very efficient, and transitions between the 6 A 1 ground state and all ligand field excited states remain largely forbidden.…”

“…6 A 1 radiative lifetime of t % 1.8 ms (i.e., k r Mn % 550 s À1 ). [66] Anion spin-orbit contributions decrease this radiative lifetime by a factor of 8 in ZnSe, to t % 0.2 ms. [60] Despite the nuclear distortion of the 4 T 1 excited state, the large energy gap ($2.1-2.2 eV) between this state and the ground state disfavors nonradiative multiphonon relaxation. [67] In dilute Mn 2þ -doped ZnS nanocrystals, a very long and essentially purely radiative 4 T 1 lifetime of t ¼ 1.9 ms has been reported at 300 K, [68] and in core/shell structures such as Mn 2þ :CdS/ZnS nanocrystals a single-exponential decay time of t ¼ 4.2 ms at 12 K has been reported, [69] allowing the encouraging conclusion that non-radiative decay channels can be effectively eliminated even in such small crystallites.…”

The DV-Xα Molecular-Orbital Calculation Method

“…The other is the theoretical prediction of the lifetime of a Mn 2+ emission. For single crystals of II-VI compounds doped with Mn 2+ ions, the lifetime of a Mn 2+ emission was accurately reproduced by cluster calculations (Boulanger et al 2004). Accordingly, theoretical calculations are applicable to determine the lifetime of Mn 2+ emissions in various compounds.…”